Coincidentally, Hawking died on Albert Einstein's birthday. Einstein, another venerated theoretical physicist, also died at age 76, in 1955.

March 14 is also Pi Day in the US, in honor of the mathematical constant whose first digits are 3.14.

Skye Gould/Business Insider

Hawking was known around the world for making discoveries that transformed the way scientists think about black holes and stellar systems. He was also beloved for his wit and humor in expressing profound concepts to the public.

He's survived by his three children, Lucy, Robert, and Tim. They released a statement calling their father an "an extraordinary man whose work and legacy will live on for many years."

"He once said, 'It would not be much of a universe if it wasn't home to the people you love.' We will miss him forever," their statement said.

Well-known physicists including Neil deGrasse Tyson and Lawrence Krauss have also made statements on Wednesday expressing admiration for Hawking.

"His passing has left an intellectual vacuum in his wake," Tyson said on Twitter. "But it's not empty. Think of it as a kind of vacuum energy permeating the fabric of spacetime that defies measure."